linter: undo ignoring single stmts in prefer-robust-stmts aka #231 (#902)

Author: sbdchd

crates/squawk_linter/src/ignore.rs

@@ -301,6 +301,25 @@ create table users (
                     },
                 ),
             },
+            Violation {
+                code: PreferRobustStmts,
+                message: "Missing `IF NOT EXISTS`, the migration can't be rerun if it fails part way through.",
+                text_range: 14..31,
+                help: None,
+                fix: Some(
+                    Fix {
+                        title: "Insert `if not exists`",
+                        edits: [
+                            Edit {
+                                text_range: 24..24,
+                                text: Some(
+                                    " if not exists",
+                                ),
+                            },
+                        ],
+                    },
+                ),
+            },
             Violation {
                 code: BanCharField,
                 message: "Using `character` is likely a mistake and should almost always be replaced by `text` or `varchar`.",

crates/squawk_linter/src/rules/prefer_robust_stmts.rs

@@ -19,18 +19,6 @@ pub(crate) fn prefer_robust_stmts(ctx: &mut Linter, parse: &Parse<SourceFile>) {
     let mut inside_transaction = ctx.settings.assume_in_transaction;
     let mut constraint_names: HashMap<Identifier, Constraint> = HashMap::new();
 
-    let mut total_stmts = 0;
-    for _ in file.stmts() {
-        total_stmts += 1;
-        if total_stmts > 1 {
-            break;
-        }
-    }
-    if total_stmts <= 1 {
-        // single stmts are fine
-        return;
-    }
-
     enum ActionErrorMessage {
         IfExists,
         IfNotExists,
@@ -512,22 +500,6 @@ CREATE TABLE "core_bar" (
         );
     }
 
-    #[test]
-    fn ignore_single_stmts_ok() {
-        // we don't include a placeholder stmt because we're actually checking
-        // for the single stmt behavior here
-        let sql = r#"
-CREATE INDEX CONCURRENTLY ON "table_name" ("field_name");
-        "#;
-        lint_ok_with(
-            sql,
-            LinterSettings {
-                assume_in_transaction: true,
-                ..Default::default()
-            },
-        );
-    }
-
     #[test]
     fn create_index_concurrently_without_name_ok() {
         let sql = r#"